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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0284-signal-Prevent-double-free-of-user-struct.patch | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/debian/patches-rt/0284-signal-Prevent-double-free-of-user-struct.patch b/debian/patches-rt/0284-signal-Prevent-double-free-of-user-struct.patch new file mode 100644 index 000000000..8a50b4089 --- /dev/null +++ b/debian/patches-rt/0284-signal-Prevent-double-free-of-user-struct.patch @@ -0,0 +1,52 @@ +From 9a8853e64ab5f1c44db176464996da3ba86d2a8e Mon Sep 17 00:00:00 2001 +From: Matt Fleming <matt@codeblueprint.co.uk> +Date: Tue, 7 Apr 2020 10:54:13 +0100 +Subject: [PATCH 284/323] signal: Prevent double-free of user struct +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +The way user struct reference counting works changed significantly with, + + fda31c50292a ("signal: avoid double atomic counter increments for user accounting") + +Now user structs are only freed once the last pending signal is +dequeued. Make sigqueue_free_current() follow this new convention to +avoid freeing the user struct multiple times and triggering this +warning: + + refcount_t: underflow; use-after-free. + WARNING: CPU: 0 PID: 6794 at lib/refcount.c:288 refcount_dec_not_one+0x45/0x50 + Call Trace: + refcount_dec_and_lock_irqsave+0x16/0x60 + free_uid+0x31/0xa0 + __dequeue_signal+0x17c/0x190 + dequeue_signal+0x5a/0x1b0 + do_sigtimedwait+0x208/0x250 + __x64_sys_rt_sigtimedwait+0x6f/0xd0 + do_syscall_64+0x72/0x200 + entry_SYSCALL_64_after_hwframe+0x49/0xbe + +Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> +Reported-by: Daniel Wagner <wagi@monom.org> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/signal.c | 4 ++-- + 1 file changed, 2 insertions(+), 2 deletions(-) + +diff --git a/kernel/signal.c b/kernel/signal.c +index e1f263cbcf09..a1eeecb4922d 100644 +--- a/kernel/signal.c ++++ b/kernel/signal.c +@@ -495,8 +495,8 @@ static void sigqueue_free_current(struct sigqueue *q) + + up = q->user; + if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) { +- atomic_dec(&up->sigpending); +- free_uid(up); ++ if (atomic_dec_and_test(&up->sigpending)) ++ free_uid(up); + } else + __sigqueue_free(q); + } +-- +2.43.0 + |